The present invention pertains to a technical field of laser, and particularly relates to an emission wavelength-programmable organic distributed feedback laser.
Drastic development of communication technology, typically personal computers, portable telephones, internets, etc. is called “IT revolution”, bringing radical changes to the industrial and social structures. Furthermore, as to the promotion of domestic internet prevalence, optical fibers including optical fibers of organic polymers have been already, domestically used, and thus development of low cost, high performance organic waveguide lasers capable of handling much larger amount of information in future has been in urgent need.
It is well known, on the other hand, that when a thin film of having azobenzene groups is subject to interference exposure with such a wavelength as to induce photoisomerization periodic grooves (surface relief gratings) are formed by mass transfer of the polymers on a nanometer-micrometer level (e.g. JP-A-2003-82033).
In the formation of surface relief gratings on the azobenzene polymer thin film by interference exposure, it has been reported that the polymer complexes containing functional molecules such as low molecular weight liquid crystals, etc. dispersed therein as a guest compound can increase the grating formation sensitivity by about 3 order of magnitude at the maximum as a synergistic effect of the functional molecules, so far not observable in the case of single azobenzene polymers (e.g. JP-A-2002-105339; T. Ubukata et al: Surface Relief Grating in Host-Guest Supramolecular Materials, Wiley-VCH Verlag GmbH & Co. KGaA, 2000, 12, p.1675-1678). The sensitivity has been found higher than that of the ordinary photoresist.
The periodic groove structure formed by photo-induced organic mass transfer of the azobenzene thin film has such characteristics as omission of the developing step, erasability and rewritability by light or heat, and thus the azobenzene polymers have been regarded as promising reversible, environmentally low load materials.
As to the organic distributed feedback (DFB) laser, it has been reported that laser emission is attained by periodic modulation of gains through interference photoexcitation, but in view of its application to devices the interference photoexcitation seems to be substantially impossible to conduct. Furthermore, a process for fabricating an organic DFB laser by molding has been reported, but due to the fixed laser structure the wavelength is not tunable.